Heavy pressure lubricants



L. PERAS HEAVY PRESSURE LUBRICANTS Nov. 8, 1960 2 Sheets-Sheet 1 Filed Feb. 16, 1955 FIG] 1 w 1 Q. 6 m a 6 m u m M m S F M F W W l. m 5 r fi 4. G G G o. I m 1 ml 2 F 5 F F Ski MIR k0 *imxu qmow Time in Ml'nufef FIG.

I Mefh efi x; y

' 600d Cammercl' 0i/ Mineral Oil 1 I70 Mef/vy/ 16 +1 70 M 67% 1 5 $1 24 h/oro lau r 7 Pure Mme a/ Oil Load in M/fljramj in '4 Boer/age Mac/fine w tQum R m mS o United States Patent Oiiice 2,959,552 Patented Nov. 8, 1960 HEAVY PRESSURE LUBRICANTS Lucien Pras, Billancourt, France, assignor to Regie Nationale des Usines Renault, Billancourt, France Filed Feb. 16, 1955, Ser. No. 488,533

Claims priority, application France Apr. 13, 1954 6 Claims. (Cl. 25254.6)

The lubrification of mechanical elements is most generally effected by the hydrodynamic entrainment of the oil, which iuterposes a film of oil between the metal surfaces which are subjected to relative movements with respect to one another.

It is known that, when the pressure which forces the surfaces against one another becomes too great, the hydrodynamically entrained film is broken and that in this case it is .possible to interpose an organic film between the metal surfaces by the action of chemically active fatty products which adhere strongly to the surfaces and are disposed in thin and oriented layers.

It is known that the so called unctuous films' thus constituted disappear when the working temperature rises to a value greater than that of the melting point of the iron soaps corresponding to the fatty acid, this temperature being a moderate one: of the order of 75 C. and in most cases less than the temperature generally attained by the actual mechanisms used in industry and in motor vehicles.

It is known that when the pressure increases beyond that at which the unctuous friction is ensured or when a considerable amount of slipping raises the contact temperature, the fatty film also disappears and it is necessary to resort to the so called extreme pressure" addiing from taking place when the loads or the amount of slipping are very great. In severe friction conditions, the needs have been met with sulphurated and chlorinated products of the extreme pressure types, ad-

mitting that if unctuosity is not ensured the friction temperature under moderate loads rises in sucha manner that the extreme pressure additives finally come into action, their activity being perceptible as soon as the temperature reaches a certain value.

But .thi's temperature necessary for their action is only reached after the parts have undergone some irremediable damage; this is particularly the case with new mechanisms where, owing to irregularities in .machining and assembly, very variable moderate or very strong pressures are encountered at various points. It

is important for the efficient later use of these mechanisms that running-in by abrasion or deformation should take place gradually without any seizing or tearing of the metal taking place.

In order to raise the critical temperature at which the unctuous lubricant ceases to act, it has beentried to incorporate with the oils fatty products of high molecular weight having as high a number of carbon atoms as possible so that the melting point of the corresponding soap be raised. The preparation of these products was very much hindered by the small number of natural raw materials, since the most common natural products contains but 18 carbon atoms, and by the difliculty of syntheses. Moreover, in order to increase the range of action of the lubricant against pressure, it was quite naturally proposed to mix the extreme pressure products and the unctuous products together, but when these mixtures are made it is found that the unctuous properties of the fatty esters are totally or partially inhibited.

According to the present invention, new lubricants have now been found, whose unctuosity ensures a very low co-efficient of friction and which maintain this unctuosity at a much higher temperature than those which could be reached with hitherto known lubricants.

Furthermore the new lubricants have the remarkable property of both being unctuous and at the same time of ensuring resistance to seizing under strong pressure. The products according to the invention are constituted by mixing with mineral oils or any other complex mixture of inactive hydrocarbons such as are obtained in distillations from coal for example, a long chain fatty ester having a number of carbon atoms greater than 12 and a straight chain fatty ester comprising '4 halogen atoms of which 3 are fixed at the chain end opposite the ester group and 1 in position 2 with respect to the chlorinated terminal group. Methyl tetrachlorolaurate Cl CCH -CHCl(CH CO CH is particularly suitable; it has the greater industrial advantage that it can be prepared easily, with a high efficiency, from undecylenic acid which is itself obtained industrially by cracking castor oil; the reaction is carried out with a good yield when carbon tetrachloride is caused to react on undecylenic acid in the presence of benzoyl peroxide acting as a catalyst.

The new properties of the lubricant according to the invention are revealed by laboratory measurements made on the Herschell apparatus, wherein for mean contact pressures of 15 kg./mm. the coeflicients of friction have been measured in a test comprising the entrainment of three balls, bound up in the same set of equipment, by a metallic disc turning in its plane about its axis.

The driving torque of the balls, proportional of the co-eflicient of friction, is measured by opposing thereto the torque of a spiral spring. When the equipment set is wetted with a pure mineral oil, there is no stable position of the needle connected to the opposing spring. There is a rapid succession of dry drive and of lubricated friction. The co-eflicient of friction varies between 0.15 and 0.19. The friction becomes stable when the oil contains either a fatty ester or the mixture according to the invention, but -in the first case stability disappears at a lower temperature than in the second case.

The co-efficients of friction and their variations as a function of temperature are represented in the curves in Figs. 1 to 9. Each curve represents the variation of the co-efiicient of friction as a function of time (in minutes) in'one experiment, the experiments varying from one to the'other in temperature or nature of product.

Figs. 7 to 9 inclusive concern a known mixture of 1% methyl stearate in mineraloil. The curves of Figs. 1 to 6 relate to a mixture according to the inventioncontaining 1% methyl stearate and 0.2% methyl tetrachlorolaurate. Finally, Fig. 10 represents the variation of the-co-efficient of friction as a function of temperature in the case of each of these two mixtures.

The division of each curve into two branches takes place at the instant when the friction becomes non-uniform and therefore the entrainment of the balls by the plate becomes irregular and results in an oscillatory phenomenon. It appears clearly that, with the known fatty esters, all unctuosity disappears at about 75 C.; this unctuosity still persists with the new products as far as 115 C.; this is particularly valuable in practice since the working temperature of very numerous mechanisms lies within the range 75 C.-1l5 C.

The resistance to seizing under heavy loads is shown by the measurements made on the Boerlage 4-ball machine, wherein the pressure amounts to between 250 and 500 kg./mm. with the fatty esters which use was already known and with the products according to the invention.

The curves in Fig. 11 show the variation of the seizing delay in kilogrammes in the Boerlage machine, as a function of the loads; the curve corresponding to a mixture according to the invention containing 1% methyl stearate and 1% methyl tetrachlorolaurate is close to the mean curve which would be obtained with most of good commercial oils constituted solely for the purpose of providing protection against seizing at all pressures but having no unctuous property.

The mixture which has just been mentioned for its resistance to seizing contains more halogenated products than the preceding mixture which was mentioned by way of example for the measurement of the co-efiicient of friction at moderate load; in this latter measurement the products have identical behaviour.

The non-halogenated fatty product is not necessarily methyl stearate; it may as well be resorted to the ethyl ester or any other ester, or to esters of any other fatty acids. Palmitic esters, for example, are suitable.

The new lubricants can be used with advantage in all mechanisms which do not include frictionally-driven devices, for example gearbox synchronisation devices, necessitating a high co-etiicient of friction. They are used, for example for the lubrication of internal combustion engines in the running-in period and for the permanent lubrication of transmission members, gear boxes, bevel gears, etc. They considerably reduce the wearing rate and increase the output by reducing the co-efficient of friction.

Since the heat caused by friction is reduced, the temperature reached by the oil is moderate and the amount of deterioration caused by heat remains slight. Such a lubricant has a much longer useful life than currently obtainable oils which do not benefit from the additions according to the invention.

In the case of an engine being run in, moderate contents of halogenated products will be used so as to avoid corrosions which could result from the formation of a small quantity of hydrochloric acid at the high temperatures which certain parts of the engine attain.

In transmission parts, it will be advantageous to increase the content of halogenated products. A content of 1% is very suitable.

It is possible to produce in accordance with the present invention extreme pressure lubricants at a very low price for providing very effective opposition to seiz-- ing, by incorporating, in the lubricants already constituted having a basis of mineral oil or inert hydrocarbons, the already described tetrahalogenated products in a proportion of between 1 to 8%. Such lubricants are able to ensure the regular running of hypoid gears, for example.

I claim:

1. A lubricating composition effective to provide between surfaces in frictional contact a film which will lubricate said surfaces at all pressures, comprising a major proportion of a lubricating oil having incorporated therein 0.2 to 2% of a member of the group consisting of the methyl and ethyl esters of palmitic acid and the methyl and ethyl esters of stearic acid and 0.1 to 2% of the methyl ester of tetrachlorolauric acid in which 3 chlorine atoms are attached to the terminal carbon atom opposite the carboxyl group and the other chlorine atom is attached to the carbon atom second from said terminal carbon atom.

2. A lubricating composition effective to provide between surfaces in frictional contact a film which will lubricate said surfaces at all pressures, comprising a major proportion of a lubricating oil having incorporated therein 0.2 to 2% of methyl stearate and 0.1 to 2% of the methyl ester of tetrachlorolauric acid in which 3 chlorine atoms are attached to the terminal carbon atom opposite the carboxyl group and the other chlorine atom is attached to the carbon atom second from said terminal carbon atom.

3. A lubricating composition effective to provide between surfaces in frictional contact a film which will lubricate said surfaces at all pressures, comprising a major proportion of a lubricating oil having incorporated therein 0.2 to 2% of ethyl stearate and 0.1 to 2% of the methyl ester of tetrachlorolauric acid in which 3 chlorine atoms are attached to the terminal carbon atom opposite the carboxyl group and the other chlorine atom is attached to the carbon atom second from said terminal carbon atom.

4. An extreme pressure lubricating composition effec' tive to provide between surfaces in frictional contact a film which will resist seizing at high pressures comprising a major proportion of a lubricating oil having incorporated therein 1 to 8% of the methyl ester of tetrachlorolauric acid in which 3 chlorine atoms are attached to the terminal carbon atom opposite the carboxyl group and the other chlorine atom is attached to the carbon atom second from said terminal carbon atom, and 0.2 to 2% of ethyl stearate.

5. An extreme pressure lubricating composition effective to provide between surfaces in frictional contact a film which will resist seizing at high pressures comprising a major proportion of a lubricating oil having incorporated therein 1 to 8% of the methyl ester of tetrachlorolauric acid in which 3 chlorine atoms are attached to the terminal carbon atom opposite the carboxyl group and the other chlorine atom is attached to the carbon atom second from said terminal carbon atom, and 0.2 to 2% of a member of the group consisting of the methyl and ethyl esters of palmitic acid and the methyl and ethyl esters of stearic acid.

6. An extreme pressure lubricating composition effective to provide between surfaces in frictional contact a film which will resist seizing at high pressures comprising a major proportion of a lubricating oil having incorporated therein 1 to 8% of the methyl ester of tetrachlorolauric acid in which 3 chlorine atoms are attached to the terminal carbon atom opposite the carboxyl group and the other chlorine atom is attached to the carbon atom second from said terminal carbon atom, and 0.2 to 2% of methyl stearate.

References Cited in the tile of this patent UNITED STATES PATENTS 1,944,941 Lincoln et al. Jan. 30, 1934 2,183,294 Lincoln et al. Dec. 12, 1939 2,272,470 Lincoln et al. Feb. 10, 1942 2,425,426 Joyce Aug. 12, 1947 2,812,307 Saives Nov. 5, 1957 OTHER REFERENCES Scientific Lubrication, January 1950, pages 2, 3 and 6. 

1. A LUBRICATING COMPOSITION EFFECTIVE TO PROVIDE BETWEEN SURFACE IN FRICTIONAL CONTACT A FILM WHICH WILL LUBRICATE SAID SURFACES AT ALL PRESSURES, COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL HAVING INCORPORATED THEREIN 0.2 TO 2% OF A MEMBER OF THE GROUP CONSISTING OF THE METHYL AND ETHYL ESTERS OF PALMITIC ACID AND THE METHYL AND ETHYL ESTERS OF STEARIC ACID AND 0.1 TO 2% OF THE METHYL ESTER OF TETRACHLOROLAURIC ACID IN WHICH 3 CHLORINE ATOMS ARE ATTACHED TO THE TERMINAL CARBON ATOM OPPOSITE THE CARBOXYL GROUP AND THE OTHER CHLORINE ATOM IS ATTACHED TO THE CARBON ATOM SECOND FROM SAID TERMINAL CARBON ATOM.
 4. AN EXTREME PRESSURE LUBRICATING COMPOSITION EFFECTIVE TO PROVIDE BETWEEN SURFACES IN FRICTIONAL CONTACT A FILM WHICH WILL RESIST SEIZING AT HIGH PRESSURES COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL HAVING INCORPORATED THEREIN 1 TO 8% OF THE METHYL ESTER OF TETRACHLOROLAURIC ACID IN WHICH 3 CHLORINE ATOMS ARE ATTACHED TO THE TERMINAL CARBON ATOM OPPOSITE AND CARBOXYL GROUP AND THE OTHER CHLORINE ATOM IS ATTACHED TO THE CARBON ATOM SECOND FROM SAID TERMINAL CARBON ATOM, AND 0.2 TO 2% OF ETHYL STEARATE. 